1. Field of the Invention
The present invention relates to an immersion objective lens in a device which monitors and measures a sample with use of the immersion objective lens, a retention mechanism for holding an immersion medium, and a manufacturing method thereof.
2. Description of the Related Art
When a sample in a micro-plate set on a sample stage is observed or measured by use of an immersion objective lens, an immersion medium is supplied to the tip of the objective lens, and the sample is observed and measured through the immersion medium and the bottom glass of the micro-plate. Water or immersion oil is used as this immersion medium.
The specification of U.S. Pat. No. 6,071,748 discloses a technique concerning a fluorescence correlation microscopy apparatus. In this apparatus, light is irradiated on a sample through an immersion objective lens from the lower surface of a micro-plate, and fluorescence from the sample is detected. Meanwhile, the micro-plate has many wells to contain samples, provided at positions spatially apart from one another. Therefore, measurement using a micro-plate involves a wide observation range and a long distance movement in the horizontal direction. Therefore, as a measurement area shifts, an immersion medium at the tip portion of the lens sticks to the bottom plate of the micro-plate and is scattered, in some cases. If measurement takes a long time, drying is accelerated and the immersion medium is lost since a strong laser beam runs through the objective lens for a long time, in other cases.
Hence, the pamphlet of International Publication No. WO 02/093232 discloses a device for supplying an immersion medium which supplies a large amount of immersion medium.